Recovery of resins and hydrocarbons from resinous type coals



Nov. 28, 1961 E. M. CRAIGHEAD ETAL 3,010,707

RECOVERY OF RESINS AND HYDROCARBONS FROM RESINOUS TYPE COALS 2 Sheets-Sheet 1 Filed July 20, 1959 N UP INVENTOR E. M. CRA IGHEAD HEINO PURRE ATTORNEYS 1961 E. M. CRAIGHEAD ETAL 3,010,707

RECOVERY OFRESINS AND HYDROCARBONS FROM RESINOUS TYPE GOALS Filed July 20, 1959 2 Sheets-Sheet 2 l2 6 XCENTER WELL RING WELLS FIG. 4

INVENTORS. E. M. CRAIGHEAD HEINO PURRE w fz y ATTORNEYS United States. Patent ()fiice r 3,010,707 Patented Nov. 28, 1961' 3,010,707 RECOVERY OF RESINS AND HYDROCARBONS FROM RESINOUS TYPE COALS Emery M. Craighead and Heino Purre, Bartlesville, Okla, assignors to Phillips Petroleum Company, a corporation of Delaware Filed July 20, 1959, Ser. No. 828,269 4 Claims. (Cl. 262-3) This invention relates to the production of resins and hydrocarbons from resinous type coals in situ.

Resinous coal deposits exist in several areas of the United States such as the coal deposit in Emery County, Utah. The problem of producing this type of coal without mining the same is complicated by the fact that the coal is non-porous and completely impervious or impermeable. Hence the usual process for recovering carbonaceous deposits by in situ combustion or distillation are not applicable to such coal. This invention is concerned with a method or process for recovering resin and hydrocarbon material from such a resinous fuel deposit without mining the coal. 7

Accordingly, it is an object of the invention to provide a process for the in situ production of resins and bydrocarbons from an impermeable coal vein or deposit. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

' We have found that resin can be recovered in situ from a resinous type coal vein by contacting the coal underground with steam at a temperature of at least about 550 and up to 700 or 800 F. 'In one case, heating a resinous coal sample to 590 F. for 2%. hours with saturated steam at a pressure of 1350 p.s.i.g. reduced the weight of the sample between 5 and 6 percent and produced a substantial amount of resin in' the form of light yellow liquid, as well as a substantial amount of gaseous hydrocarbon material. Another sample of the coal amounting to 305.9 grams was heated to 680 F. for 12 hours with steam and suffered a weight loss of more than 17 percent and yielded 1.5 liters of gas at 200 p.s.i.g. at room temperature, corresponding to a yield of 2200 sci/ton of raw resinous coal. The sample yielded 26 cc. of a light yellow oil and resin, equivalent to a yield of 20 gals. per ton. The residual material was a highly permeable porous mass amounting to about 83 weight percent of the original sample. The permeability of the residual coal was approximately 300 md. (millidarcies). It has been found that a permeability of 50 md. is sufficient to permit production of a carbonaceous deposit by in situ combustion wherein a combustion front is driven thru the carbonaceous material by feeding air thereto after igniting same, as in the production of oil and-tar sands by in situ combustion.

The liquid resin obtained by the distillation has been found useful in paints and varnishes and has other uses peculiar to these resins. The gas produced during the steam contacting had the following analysis as determined by mass spectrometer.

The residual carbonaceous material has ample permeability and porosity to permit recovery of further valuable hydrocarbons and fuel gas therefrom by in situ combustion. The recovery process may be effected in various ways which are better understood by reference to the accompanying schematic drawing of which FIGURE 1 is an elevation showing an arrangement of boreholes and apparatus in a coal seam suitable for effecting the process of the invention; FIGURE 2 is a similar elevation showing another arrangement for effecting another embodiment of the invention; FIGURE 3 is a plan of a ring type well pattern utilizing 9 walls; and FIGURE 4 is an elevation in partial section of a coal stratum similar to FIGURE 2. 7

Referring to FIGURE 1, a coal vein 10 is penetrated by boreholes 12 and 14 which are cased to the approximate upper surface of the coal vein by casings 16 and 18, respectively, a tubing string 20 extends to a level near the bottom of hole 12 thru well head 22 and a tubing string 24 is similarly positioned thru well head 26. Lines 28 and 30 connect with casings 16 and'18, respectively.

' In producing coal seam 10, steam is injected into boreholes 12 and 14 thru lines 28 and 30 and the uncondensed steam and produced fluids are vented thru tubing strings 20 and 24. The steam is injected at a temperature in the range of 550 to 800 and has the etfect of liquefying the solid resins in the coal which flow to the bottom of the well and are produced thru the tubing string'because of the injection pressure and the venting of the well therethru. In applications in which the coal vein is sufliciently deep, the injection pressure of the steam may be maintained sufliciently high to maintain the steam in satu rated condition which increases the rate of applying heat to the coal In coal seams which are not sufiiciently deep to allow the necessary injection pressure to maintain the steam saturated, superheated steam is used.

The steam and heat have a similar eifect in removing resins and carbonaceous material from the coal to the leaching of salt by water from a salt formation. As the heating and injection of steam is continued, the coal be comes porous and the recovery of resin and hydrocarbon material from deeper in the coal around the borehole: continues. This process is continued until the two porous areas 32 and 33 around the two boreholes 12 and 14, respectively, meet as at 34. This renders it feasible to initiate combustion of the residual porous coal around one of the boreholes, followed by driving the resulting combustion zone to the other borehole by feeding a combustion-supporting gas, such as air, oxygen-enriched air, or these gases containing between 1 and 4 volume percent of fuel gas. As in the in situ combustion of an oil formation, the combustion front may be driven thru the porous. formation by either direct or inverse'drive. Utilizing direct drive, after initiating combustion by conventional methods around borehole 14, the combustion-supporting gas isinjected thru hole 14 (as thru either tubing 24 or line '30) to feed the combustion front and drive the produced fluids into well 12. When utilizing inverseair injection, the air is injected thru hole 12, passing thru the porous coal to the combustion front around hole 14 and moving the front toward hole 12. During the 'combus tion, the resins and other hydrocarbon material in' the non-porous areas 36 and 38 between the boreholes ar produced by the heating and the combustion. I Y

While onlya pair of boreholes 12 and 14 is shown, borehole 14 may be centrally located within a ring of boreholes 12, similar to a 5, 7 or '9-spot well pattern utilized in the production of oil. It is also 'feasible'to produce the resin and gaseous hydrocarbons from a series of in-line boreholes 12 and 14, and, also, another is illustrated in FIGURE 4. 'jected into the fractures thruthe perforations 60 in the line of boreholes on the opposite side of 1-4 from 12 may be used so that, after producing sufficient resin and gaseous material from the deposit around the three lines of boreholes to provide a porous passageway therebetween, combustion may be initiated around wells 14 in the intermediate line of boreholes and the resulting combustion front may be driven outwardly toward the ad-' jacent lines of boreholes as in a line drive pattern of producing oil wells by in situ combustion.

The arrangement in FIGURE 2 comprises a pair of boreholes 40 and 42 provided with casings 41 and 43 and with tubing strings 44 and 46, respectively. Lines 48 and 50 connect with the casings 41 and 43, respectively. Coal vein' is fractured between boreholes 40 and 42. at two different levels 52 and 54 in conventional manner so thatsteam can be passed between boreholes thruthe fractures. Packers 56 and 57 on tubing string 44 pack off the borehole 40 between the fractures and similar packers 58 and 59 pack off borehole 42.between the fractures.

In producing resin and gaseous products from coal vein 10 with the arrangement of FIGURE 2 steam is injected thru tubing string 44 and line 48 so as to pass same thru fractures 52 and 54 to borehole 42. Steam and products passing into borehole 42 from fracture 54 are vented thru tubing string 46. Packers 56, 57, 58, and 59 need not be positioned in the boreholes until after the initial production phase of the process in which the resin and gaseous products are removed from 'the entire area between the fractures so as to render the same permeable to gas. When this has been accomplished, the packers are located as shown and in situ combustion is established in the coal vein along one of the fractures, such as 52. Thereafter, combustion-supporting gas, such as air,-is injected thru either lines 48 and 50 to drive the combustion front by direct drive to fracture 54, with production being recovered thru tubing strings 44 and 46. It is also feasible to inject the combustion-supporting gas thru tubing strings 44 and 46 to move the combustion front from fracture 52 to fracture 54 inversely to the flow of gas to produce hydrocarbon-containing gases thru lines'48 and 50.

Instead of utilizing packers, as shown, it is also feasible to case the boreholes 40 and 42 to the bottom of the coal seam and perforate the casings at the desired fracture levels for the fracturing-step. This technique In this case, steam is incasing 41 and production is recovered thru the perforations 62 in the opposite casing 43. After the initial phase of, the production in which resins are recovered and the intervening coal (between fractures 52 and 54) is made permeable, the perforations in the casing in one borehole are plugged with cement in conventional manner at one level and the perforations in the opposite casing at the other level are plugged in similar manner so that air injected at one level cannot pass thru the fracture directly into the other casing, but must go thru the porous coal into the opposite fracture in order to 'pass thru the open perforations at this level. In this manner, an in situ combustion front may be driven vertically thru the porous coal from one fracture to the other, without using packers.

While two boreholes are shown in FIGURE 2, the ting type pattern and the in-line drive pattern described in'connection with FIGURE 1 may also be utilized. FIGURE 3 illustrates a ring type pattern comprising 8 wells 14 in a ring surrounding a central well 12.

Certain modifications of the invention will become apparent to .those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on 'the invention.

We claim 1. A process for producing resin and fuel gas from a resinous impervious coal deposit in situ which comprises establishing communication with said deposit from ground surface thru. spaced-apart first and second boreholes; horizontally fracturing said deposit at upper and lower levels therein between said boreholes to establish passageways from the first borehole to. the second borehole; passing steam at a temperature of at least 550 F. thru said passageways from said first borehole to the said second borehole so as to produce. resin and fuel gas from the coal intermediate said passageways and render said coal permeable; continuing the passing, of steam thru said passageways until said deposit is permeable from one passagewayto the other, thereby preparing the intervening permeablematerial for moving an in situ combustion front from passageway to passageway; recovering produced resin and fuel gas from said second borehole thereafter establishing in situ combustion in the residual porous material along one of said passageways; moving the resulting combustion front thru the permeable material to the other passageway by passing combustionsupporting gas to saidfront thru'one of said passageways and venting produced gases thru the other passage- Way; and recovering the produced gases from said other passageway thru one of said boreholes.

2. The process of claim 1 wherein said first borehole is surrounded by a ring of said second boreholes; said coal is fractured at both said levels to provide passageways between the boreholes in said ring and the central borehole; and said combustion front is moved vertically thru the annulus between said ring and saidcentral borehole. Y

3. The process of claim 1 wherein each borehole is cased to the upper'level of said deposit, each casingis provided with a well head and a tubing string extending therethru to substantially thelevel of the lower fracture, the section of each borehole intermediate the fracture levels is packed ofi, wherebythe gas injected into the "deposit at one fracture level produces thru the other fracture level and avoids short'circuiting into each borehole intermediate thefracture levels.

4. The process of claim 1 wherein each borehole is cased to the lower level of said deposit and each casing is provided with a wellhead and conduit means leading therethru; and including the steps of perforating each said casing at said upper level and at said lower level; effecting said fractures thru the resulting perforations; after said deposit is made permeable from one passageway to the other, sealing the perforations in one casing at the upper level and sealing the perforations in the other casing at the lower level to limit the passageway for gas from casing to casing-thru the perforations in one casing at one level into the fracture at said one level, fromsaid fracture generally vertically thru said deposit tothe other fracture, and thence thru the perforations in the other casing; thereafter igniting said perrneable material along one of said fractures; and injecting combustion-supporting gas thru the perforations in one of said casings to feed the resulting combustion front and withdrawing produced gases thru the perforations in the other casing, thereby moving said combustion front substantially vertically thru the permeable material intermediate said passageways.

' References Cited in the file of this patent Hurley Nov. 1, 1960 

